Histoplasma capsulatum in wild mammals from Ecuador

Abstract

Background Histoplasma capsulatum is a globally distributed dimorphic fungal pathogen endemic to the Americas, Africa, and Asia. It causes histoplasmosis, a disease acquired via inhalation of spores from contaminated environments. It thrives in nitrogen-rich soils and is disseminated by avian and chiropteran reservoirs. Histoplasma capsulatum has been found in wild mammals such as rodents, marsupials, felines, and xenarthrans, suggesting diverse reservoirs that may influence its maintenance and transmission in endemic areas. This study aimed to detect H. capsulatum in tissues of wild small mammals sampled across Ecuador. Methods Tissue samples (n=324) were collected from wild mammals across the Coast, Andean, and Amazon regions between 2022 and 2023. Species were identified morphologically and H. capsulatum was detected using nested PCR targeting the 100-kDa protein-encoding gene. Positive samples were sequenced and analyzed. Ecological niche modeling focused on environmental clustering, via one class support vector machine (OC-SVM) hypervolumes, identified regions suitable for fungal survival. Results H. capsulatum was detected in 14% of samples in 30 of 106 species studied, predominantly in Chiroptera (80%) followed by Rodentia (15%) and Didelphimorphia (4%). Suitable environmental conditions were concentrated in Ecuador’s Coast region with isolated patches in the Andean and Amazon regions. Conclusion This study documents the broad host range and ecological distribution of H. capsulatum in Ecuador, reinforcing concerns about its zoonotic potential. The detection of the fungus across diverse mammalian taxa and ecosystems emphasizes the importance of wildlife-based surveillance to better understand fungal pathogen reservoirs and geographic hotspots.